Ionic, The pipe 'translate' could not be found, only in AoT Compiler - ionic-framework

Question

I have a problem with ngx-translate within a Ionic App when I try to build a production release.
During development translations work fine with
ionic serve
and
ionic cordova build android
but if I try to make a production build using
ionic cordova build android --prod --release
or for the PWA
ionic build --prod
I get some errors like
[17:47:15] typescript error
The pipe 'translate' could not be found ( ... )
Versions:
ngx-translate: 8.0.0
Ionic: 3.9.2
Angular: 5.2.10
I checked with: https://github.com/ngx-translate/core/tree/v8.0.0 and can't find what I am doing wrong.
In app.module:
// https://github.com/ngx-translate/core#1-import-the-translatemodule
// AoT requires an exported function for factories
export function createTranslateLoader(http: Http) {
return new TranslateHttpLoader( http, './assets/i18n/', '.json' );
}
#NgModule( {
...
imports: [
...
TranslateModule.forRoot( {
loader: {
provide: TranslateLoader,
useFactory: (createTranslateLoader),
deps: [ Http ]
}
}
),
...
And in one of my pages which produce this error:
import { TranslateModule, TranslateService, TranslatePipe } from '#ngx-translate/core';
#NgModule({
imports: [
TranslateModule
],
exports: [
TranslateModule
]
})
export class ContactPage { ... }
Searching through SO produced mainly the hint to import & export the TranslateModule in the page as well as importing the TranslatePipe, but both of these changes didn't solve my problem. How do I configure the translation module so that it works in a production build?

Answer 1

OK, solved it. I added the import & export statement of the TranslateModule to the page class, but correct is to add it the the corresponding module.
In my example:
Wrong:
contact.ts
#NgModule({
imports: [
TranslateModule
],
exports: [
TranslateModule
]
})
export class ContactsPage {...}
Correct:
contact.module.ts
#NgModule( {
...
imports : [
...
TranslateModule
],
exports : [
TranslateModule
]
} )
export class ContactsPageModule {
}